textproduct: Albany

WHAT HAS CHANGED

Slight risk for severe thunderstorms expanded into portions of the mid Hudson Valley for Tuesday. Also lowered max temps even further for Tue-Wed, especially from Albany north and east.

KEY MESSAGES

1) Low pressure system and approaching warm front bring showers and non-severe thunderstorms late tonight into Tuesday morning with locally heavy rainfall.

2) A few strong to severe thunderstorms possible south and west of the Capital Region Tuesday afternoon into the evening with an isolated flash flood threat for the region.

3) Additional rounds of showers and thunderstorms Wednesday into Thursday with some strong thunderstorms and isolated to scattered instances of heavy rainfall/flash flooding possible.

DISCUSSION

KEY MESSAGE 1...

Approaching warm front and upper level shortwave from the west will bring increasing coverage of showers this evening and overnight, with some embedded thunderstorms developing after midnight and continuing through Tuesday morning. PWAT's increase overnight to 1.75 to just under 2 inches, along with forcing from approaching upper level shortwave as well as developing dual upper level jet structure (one upper jet across northern Maine, another approaching from Great Lakes region) should allow for some heavier bands of showers to develop later tonight. Some weak elevated instability could also allow for a few embedded thunderstorms. Rainfall rates of 0.50-1"/hour could occur.

It appears that heaviest rain potential might be near or north of I-90 around daybreak Tuesday where best forcing overlaps deep moisture, before shifting south and east during Tuesday morning. Will have to watch for ponding of water in low lying/poor drainage and urban areas for the Tuesday morning commute, with isolated flash flooding possible. Showers/thunderstorms should then shift south of the region by midday with areas of drizzle then lingering.

KEY MESSAGE 2...

Additional showers/thunderstorms are expected Tuesday afternoon as some surface based instability develops, mainly for areas south and west of Albany. 12Z/HREFs suggest MU CAPES of 1000-2000 J/kg may develop in these areas by late Tuesday afternoon, amid 0-6 km shear of 30-40 KT, with greatest overlap across the SE Catskills and mid Hudson Valley, which is where the Slight Risk for severe thunderstorms has been included for Tuesday afternoon. Latest CAMs suggest some potential for supercell development across the mid Hudson Valley region Tuesday afternoon, with isolated to scattered instances of large hail and damaging winds possible. Given enhanced low level shear across portions of the mid Hudson Valley and NW CT in close proximity to an effective warm frontal boundary (possibly reinforced from earlier convective outflow), can not rule out a tornado or two in the mid Hudson Valley region as well. Showers/thunderstorms may eventually shift south and east of the region Tuesday evening as forcing and instability decrease further.

KEY MESSAGE 3...

Stronger upper level shortwave approaches from the Great Lakes, along with surface occluded front late Wednesday into Thursday. Although much of Wednesday may just be cloudy with only spotty showers or drizzle and rather cool temperatures in the 60s/lower 70s, areas of rain and embedded thunderstorms are expected to develop Wednesday evening and continue into Thursday. Main concern during this time period will be additional locally heavy rain, especially should it coincide spatially with areas which receive antecedent heavy rainfall. An area of Slight Risk for Excessive Rainfall will be located across the Mohawk Valley, SW Adirondacks and upper Hudson Valley region with a Marginal Risk for the remainder of the region. Surface based instability may remain limited to the westernmost Mohawk Valley, eastern Catskills and perhaps mid Hudson Valley, however elevated instability should allow for a few embedded thunderstorms, especially areas west of the Hudson River Valley. Should any breaks in the clouds occur Wednesday through Thursday, a few stronger thunderstorms can not be ruled out, especially across portions of the Mohawk Valley, mid Hudson Valley and NW CT given the strong mid level winds (40-50 KT) expected across the area.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18z Tuesday...VFR conditions currently prevail across all terminals this afternoon, though clouds are continuing to increase across the region ahead of a complex system. Some light showers have also crossed into our CWA boundary, approaching ALB/PSF/POU per latest scans of the ENX radar, but high dew point depressions seem to be keeping most of the precipitation elevated. There could be a couple of instances of some light rain or drizzle in a couple of hours, particularly at POU and PSF, but VFR conditions are not expected to be deviated from.

That said, as this afternoon becomes this evening and tonight, clouds will continue to thicken with ceilings developing and lowering as deep-layer moisture increases. More widespread rain showers will also move into the area, worsening conditions into the MVFR category everywhere. With ample moisture, it's likely that both visibility and ceiling heights will drop into the MVFR category initially. However, as moisture continues to increase and rain potentially gets moderate, ceilings at least will fall into the IFR category. IFR visibility will be possible, but confidence was not high enough in this element of the forecast to include this in the TAFs at this time. This is primarily due to the uncertainty in the placement of the heaviest rainfall.

Showers continue into the morning tomorrow, potentially transitioning to thunderstorms by the end of the TAF cycle. However, due to continued uncertainty in the overall occurrence and locations of thunderstorms, we did not include thunder in the TAFs at this time. We will provide more detail in future iterations as confidence increases. Winds will prevail primarily out of the south to southeast through the duration of the 18z TAF period, with sustained speeds remaining under 10 kt. Of course, should a thunderstorm occur and track over one of the terminals, wind speeds could pick up and become breezy.

Outlook...

Tuesday Night: Moderate Operational Impact. Chance of SHRA. Wednesday: Moderate Operational Impact. Likely SHRA...TSRA. Wednesday Night: High Operational Impact. Definite SHRA...TSRA. Thursday: High Operational Impact. Likely SHRA...TSRA. Thursday Night: Low Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: Low Operational Impact. Slight Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.